ZOOKEEPER-4956: Provide a HostProvider that uses DNS SRV record for dynamic server discovery

[li4wang]

The existing ZooKeeper client architecture relies on StaticHostProvider, which lacks auto service discovery capabilities and must wait for external mechanisms to push server list updates, either through manual configuration changes or reconfig notifications.

This PR provides a HostProvider implementation that performs dynamic service discovery based on DNS SRV record and also an automatic HostProvider selection based on connection string format. The following is a summary of the changes:

1. DnsSrvHostProvider: New HostProvider implementation that performs DNS SRV lookups to discover ZooKeeper servers
2. HostConnectionManager: Extracted connection management and reconfiguration logic from StaticHostProvider into a reusable component
3. StaticHostProvider Refactoring: Modified to use HostConnectionManager for consistent connection handling across providers
4. Configuration: Added zookeeper.hostProvider.dnsSrvRefreshIntervalSeconds client property for DNS refresh intervals
5. HostProviderFactory: New factory class that checks connection strings and instantiates appropriate HostProvider based on the detected format
6. ConnectStringParser Enhancement: Extended to detect and validate DNS SRV connection string formats, adding support for dns-srv:// prefix detection
7. ZooKeeper Constructor Integration: Updated ZooKeeper constructors to use HostProviderFactory for automatic provider creation when no custom HostProvider is specified

[anmolnar]

Where are the changes of StaticHostProvider?

[li4wang]

Where are the changes of StaticHostProvider?

I thought it would be better to check in the updated StaticHostProvider later in a separate PR, as the changes are code refactoring, so I took it out from this PR.

However, I noticed that StaticHostProvider is mentioned in the summary of this PR, let me just added it back to avoid any confusion.

[li4wang]

Hi @anmolnar, thanks a lot for your feedback. I've responded to all the comments. Can you please take a look at the updated PR? Thanks.

[anmolnar]

Just a few more comments, otherwise looks good to me.

[anmolnar]

Please see my comments on the other pr #2321
I think we should merge these patches into a single one.

[li4wang]

I think we should merge these patches into a single one.

Yes, working on merging #2321 into this one right now.

[li4wang]

@anmolnar thanks a lot for your feedback. I've merged #2321 into this one and addressed all the comments. Would you mind taking a look at it? Thanks.

[anmolnar]

Overall lgtm. Just a few nitpicks.

[li4wang]

@anmolnar thanks for reviewing the updated PR. I have addressed all the comments. Would you mind taking a look at it again? Thanks.

[anmolnar]

lgtm. 🚢

[li4wang]

@anmolnar Thanks a lot for reviewing the PR and providing the feedback!